Electrolytic sn or sn alloy plating solution and method for producing sn or sn alloy plated article

ABSTRACT

The purpose of the present invention is to provide an electrolytic Sn or Sn alloy plating solution capable of lowering Pb concentration. An electrolytic Sn or Sn alloy plating solution for forming a plated article for solder bonding, at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant, wherein the sulfur-based compound is a thiol compound represented by following general formula (Formula. A), a salt of the thiol compound (Formula A), or a disulfide compound (Formula B).

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an electrolytic Sn or Sn alloy plating solution for forming a plated article for solder bonding and a method for producing an Sn or Sn alloy plated article for producing a plated article for solder bonding. The present application claims priority based on Japanese Patent Application No. 2017-178077 filed in Japan on Sep. 15, 2017, which is incorporated by reference herein.

Description of Related Art

Along with higher density and higher capacity of a device, an influence for malfunction of the device by an alpha ray generated from soldering material used for bonding with a semiconductor chip has become a problem which cannot be ignored. It is known that the alpha ray is generated mainly from Pb metal contained in the soldering material (precisely, in Sn metal) as impurities. Therefore, in the past, it is required to lower Pb concentration.

For example, in Patent Literature 1, it is described to provide a plurality of solder bumps with low Pb concentration comprised of Sn—Ag—Cu plating at a main surface of a semiconductor chip for connecting with a mounting board. In addition, in Patent Literature 2, it is described to bond by using a lead-free solder for bonding structure.

Patent Literature 1: JP 2011-040606 A

Patent Literature 2: JP 2016-103530 A

SUMMARY OF THE INVENTION

However, considering a progress of a semiconductor industry, it is considered that more miniaturization, higher density and higher capacity of the device will progress, and it will be necessary to cope with low alpha ray further, so Sn plating capable of lowering Pb concentration further will be required.

Here, the purpose of the present invention is to provide an electrolytic Sn or Sn alloy plating solution capable of lowering Pb concentration.

An electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention is an electrolytic Sn or Sn alloy plating solution for forming a plated article for solder bonding, at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant, wherein the sulfur-based compound is a thiol compound represented by following general formula (Formula A), a salt of the thiol compound (Formula A), or a disulfide compound (Formula B).

HS-R₁   Formula A:

R₂—S—S—R₂   Formula B:

R₁ is any of

R₂ is any of

In this way, it is possible to provide an Sn plated article capable of lowering Pb concentration, by inhibiting eutectoid of Pb, by functions of each component.

At this time, in one embodiment of the present invention, a ratio of concentration of the sulfur-based compound, Sn of the Sn salt, the acids or water-soluble salts thereof, and the surfactant may be 1:0.2 to700:1 to 3000:0.01 to 1000 by weight ratio.

In this way, it is possible to lower Pb concentration further, as a ratio of concentration of each component will be an optimum ratio.

In addition, in one embodiment of the present invention, the R₁ may be any of the general formulas (I) to (III), the R₂ may be the general formula (IV) or (V), and the Formula (A) or the Formula (B) may be bonded with 2-position or 6-position of the R₁ or the R₂.

In this way, it is possible to lower Pb concentration further, by inhibiting eutectoid of Pb.

In addition, in one embodiment of the present invention, the acids or water-soluble salts thereof may be one or more types of acids or salts thereof selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, organic sulfonic acid, carboxylic acid, or salt thereof, and also, the surfactant may include one or more types of surfactants selected from anionic surfactant, cationic surfactant, and non-ionic surfactant.

In this way, it is possible to lower Pb concentration further, by inhibiting eutectoid of Ph, as optimum components will be selected.

Further, it may comprise one or more types of metal salts other than Sn salt selected from Ag salt, Cu salt, Bi salt, In salt, Au salt, Sb salt, Zn salt, and Ni salt.

In this way, it is possible to provide an Sn alloy plating solution capable of lowering Pb concentration, as it will be the Sn alloy plating solution applicable for SnAg, SnCu, SnBi, SnIn, SnAu, SnSb, SnZn, and SnNi.

In addition, one embodiment of the present invention is a method for producing an Sn or Sn alloy plated article for producing a plated article for solder bonding, comprising: a plating solution preparation step for preparing an electrolytic Sn or Sn alloy plating solution; and a plating step for producing the Sn or Sn alloy plated article using the plating solution, wherein, in the plating solution preparation step, the electrolytic Sn or Sn alloy plating solution is prepared by at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant, wherein the sulfur-based compound is a thiol compound represented by following general formula (Formula A), a salt of the thiol compound (Formula A), or a disulfide compound (Formula B).

HS—R₁   Formula A:

R₂—S—S—R₂   Formula B:

R₁ is any of

R₂ is any of

In this way, it is possible to provide an Sn plated article capable of lowering Ph concentration, by inhibiting eutectoid of Pb, by functions of each component.

In addition, in one embodiment of the present invention, a film of the Sn or Sn alloy plated article may he low alpha grade Sn or Sn alloy plating film (less than 0.01 counts/hr/cm²).

In this way, it is possible to prevent an influence for malfunction of the device, as it is possible to lower Pb concentration.

As explained in the above, according to the present invention, it is possible to provide an electrolytic Sn or Sn alloy plating solution capable of lowering Pb concentration, by inhibiting eutectoid of Pb, by functions of each component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating an outline of a method for producing an Sn or Sn alloy plated article relating to one embodiment of the present invention.

FIG. 2 illustrates a relation of an amount of alpha ray and Pb content in Sn.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, explaining in detail about preferred embodiments of the present invention, with reference to the drawings. In addition, the embodiments explained in below will not unjustly limit the content of the present invention described in claims, and it is not limited that all the structures explained in the embodiments are necessary as means for solving the problem of the present invention.

1. Electrolytic Sn or Sn alloy plating solution

1-1. Sulfur-based compound

1-2. Sn salt, salts other than Sn

1-3. Acids or water-soluble salts thereof

1-4. Surfactant

1-5. Crystal regulator

1-6, Organic solvent

1-7. Antioxidant

1-8. Chelating agent 2. Method for producing Sn or Sn alloy plated article 2-1. Plating solution preparation step 2-2. Plating step

1. Electrolytic Sn or Sn Alloy Plating Solution

An electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention is an electrolytic Sn or Sn alloy plating solution for forming a plated article for solder bonding, at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant. And, the sulfur-based compound, the Sn salt, the acids or water-soluble salts thereof, and the surfactant, which are at least added, are having following characteristics. It will be explained in detail in below.

Here, a plating solution is a solution to be used for plating, that is, a solution in which various metals and components are condensed in one container, a solution in which various metals and components are divided into a plurality of containers and in which various metals and components are condensed in each container, a solution in which the condensed solution is adjusted with water to prepare initial make up of electrolytic bath, and a solution in which various metals and components are added and adjusted to prepare initial make up of electrolytic bath.

1-1. Sulfur-Based Compound

A sulfur-based compound contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention is a thiol compound represented by following general formula (Formula A), a salt of the thiol compound (formula A), or a disulfide compound (Formula 13).

HS—R₁   Formula A:

R₂—S—S—R₂   Formula B:

R₁ is any of

R2 is any of

The sulfur-based compound contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention is contained as an eutectoid inhibitor of Pb, which is a thiol compound, a salt of the thiol compound, as indicated in the Formula A, or a disulfide compound as indicated in the Formula B. And, R₁ is any of aniline (I), pyridine (II), or pyridine N oxide (III). In addition, R₂ is any of aniline (IV), pyridine (V), benzene (VI), butane (VII), or toluene (VIII). In addition, as indicated in the Formula B, R₂ having same structure are bonded at left and right.

By preparing a plating solution at least comprising an Sn salt, acids or water-soluble salts thereof, and a surfactant, as described in below, it is possible to provide an electrolytic Sn or Sn alloy plating solution capable of lowering Pb concentration, by inhibiting eutectoid of Pb, by functions of each component.

In addition, there is an optimum ratio for a ratio of concentration (g/L) of the sulfur-based compound, the Sn salt, the acids or water-soluble salts thereof, and the surfactant contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention, and the optimum ratio is 1:0.05 to 10000:0.5 to 50000:0.0005 to 10000 by weight ratio. Preferably, 1:0.2 to 700:1 to 3000:0.01 to 1000 by weight ratio, and more preferably, 1:0.2 to 140:2 to 400:0.01 to 200 by^(,) weight ratio. Further preferably, 1:4 to 16:15 to 62:0.5 to 2 by weight ratio. For example, in a scope of further preferable ratio, if the sulfur-based compound is 1, Sn of the Sn salt is 4 to 16, the acids or water-soluble salts thereof is 15 to 62, and the surfactant is 0.5 to 2 by weight ratio.

With respect to a concentration of the sulfur-based compound by weight, when a ratio of concentration of the Sn salt, the acids or water-soluble salts thereof, and the surfactant by weight is outside the above range, there is a possibility that an ability to inhibit eutectoid of Pb will be deteriorated. By adjusting to be in the above range, a ratio of concentration of each component will be in the optimum ratio, and eutectoid inhibiting ability will be increased, and it will be possible to lower Pb concentration further.

Further, a concentration of the sulfur-based compound contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention is preferably 0.01 to 100 g/L. When the concentration is less than 0.01 g/L, there is a possibility that eutectoid inhibiting ability will be decreased. On the other hand, when the concentration is more than 100 g/L, it is not preferable in terms of cost. It is more preferably 0.1 to 50 g/L, and further preferably 0.5 to 50 g/L.

The sulfur-based compound contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention functions as the eutectoid inhibitor of Pb as described above. It is because the sulfur-based compound added in the plating solution shifts a deposition potential of Sn and Pb to noble or base. (It is shifted to base side or noble side by a type of the sulfur-based compound.) It is because a compound shifting a deposition potential of Sn to base side tends to shift a deposition potential of Pb also to base side, and a compound shifting a deposition potential of Sn to noble side tends to shift a deposition potential of Pb also to noble side. It is considered that it is because a deposition potential of Sn will be more noble than a deposition potential of Pb, and also, a potential difference will be broadened more than 0.06 V at this time.

Here, in an Sn or Sn alloy plating film, Pb is contained as impurity as described above. This is because Pb is contained in the Sn salt added to a plating solution when preparing the Sn plating solution. When plating, this Pb is incorporated in Sn or Sn alloy plating. Thus, in the past, an Sn salt with low Pb concentration, in which Ph concentration is lowered in a purification stage of the Sn salt, is used, in order to lower an amount of Pb in the Sn or Sn alloy plating film. However, along with more miniaturization, higher density and higher capacity of the device as described above, it is expected that it will be required to lower Pb concentration further. In that case, it is difficult to lower Pb concentration further, as more sophisticated Sn purification technology will be necessary, and also, cost will be increased.

Here, as a result of keen examination for achieving the purpose of the present invention, the inventors have found that the sulfur-based compound used in one embodiment of the present invention inhibits eutectoid of Pb, and that other components assist to inhibit eutectoid of Pb. In other words, by at least containing the sulfur-based compound, the Sn salt, the acids or water-soluble salts thereof, and the surfactant, as the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention, the sulfur-based compound inhibits eutectoid of Pb, the Sn salt, the acids or water-soluble salts thereof, and the surfactant assist to inhibit eutectoid of Pb, so it is possible to provide the electrolytic Sn or Sn alloy plating solution capable of lowering Pb concentration, by inhibiting eutectoid of Pb. Thus, by combining the sulfur-based compound, the Sn salt, the acids or water-soluble salts thereof, and the surfactant, it is possible to achieve the above purpose comprehensively. It will be explained in detail in below.

In the sulfur-based compound, it is preferable that the R₁ is any of the general formulas (I) to the R₂ is the general formula (IV) or (V), and the Formula (A) or the Formula (B) is bonded with 2-position or 6-position of the R₁ or the R₂. By configuring as such molecule structure, sulfur atoms and nitrogen atoms in the molecule structure in aqueous solution can hold. Sn and Pb ions stronger compared to other 1, 3, 4, 5-positions. Therefore, more significant effect will be exerted also regarding potential, and it is possible to inhibit eutectoid of Ph further.

As thiol of the sulfur-based compound, it is not limited as below, but concretely, benzene thiol, 1, 4-benzene dithiol, 1, 3-benzene dithiol, 1, 2-benzene dithiol, 1, 3, 5-benzene trithiol, 2-naphthalene thiol, 1, 5-naphthalene dithiol, 4-methyl ⁻benzene thiol, 2-methyl benzene thiol, 3-methyl benzene thiol, 3, 5-dimethyl benzene thiol, 4-amino benzene thiol, 2, 4-dimethyl benzene thiol, 3, 4-dimethyl benzene thiol, 4-hydroxy benzene thiol, 3-amino benzene thiol, 4-tea-butyl benzene thiol, 2, 5-dimethyl benzene thiol, 4-ethyl benzene thiol, 3-hydroxy benzene thiol, 4-isopropyl benzene thiol, 4-methoxy benzene thiol, 2-amino benzene thiol, 4-(dimethyl amino) benzene thiol, 3-methoxy benzene thiol, toluene-3, 4-dithiol, 2-hydroxy benzene thiol, 2-ethyl benzene thiol, 2-isopropyl benzene thiol, 2-methoxy benzene thiol, 3, 4-dimethoxy benzene thiol, 5-tert-buthyl-2-methyl benzene thiol, 2, 5-diamino-1, 4-benzene thiol, 3-ethoxy benzene thiol, 4-nitro benzene thiol, 4, 4′-biphenyl dithiol, thioxylenol, 3-mercapto benzoic acid, sodium thiosalicylate, 4-acetoamide benzene thiol, 2-mercapto pyridine, 2-mercapto pyridine N-oxide, 2-mercapto pyridine N-sodium oxide, 2-mercapto-5-nitro pyridine, 2-mercapto nicotinic acid, and salts of the above compounds can be cited.

In addition, as the disulfide compound of the sulfur-based compound, it is not limited as below, but concretely, dimethyl disulfide, dimethyl trisulfide, di-tert-butyl disulfide, diethyl disulfide, diisopropyl disulfide, allyl methyl disulfide, diallyl disulfide, diisobutyl disulfide, dipropyl disulfide, methyl propyl disulfide, bis (2, 2-diethoxy ethyl) disulfide, dibutyl disulfide, diisoamyl disulfide, bis (2-dimethyl amino ethyl) disulfide, bis (2-hydroxy ethyl) disulfide, cystamine, diamyl disulfide, di-tert-octyl disulfide, didecyl disulfide, allyl propyl disulfide, tetra methyl thiuram disulfide, di-Cert-dodecyl disulfide, dicyclo hexyl disulfide, dithio diglycolate, tetra ethyl thiuram disulfide, 2, 2′-dithio dipropionate, 3, 3′-dithio dipropionate, 4, 4′-dithio dibutyrate, 3′-dithio dipropionate dimethyl, forrnamidine disulfide, tetra isopropyl thiuram disulfide, dibenzyl disulfide, methyl 2-methyl-3-furyl disulfide, tetra butyl thiuram disulfide, bis (2-mehyl-3-furyl) disulfide, bis (phenyl acetyl) disulfide, L-(-)-cystine, 2, 2′-dithienyl disulfide, DL-homocystine, 2-methyl-3-furyl propyl disulfide, 4, 4′-dithio dimorpholine, difurfutyl disulfide, 3, 3′-dithio dipropionate (N-succinimidyl), furfuryl methyl disulfide, his (2-benzamide phenyl) disulfide, N, N′-dicarbobenzoxy-L-cystine, 2, 2′-dithio his (5-nitro pyridine), 6, 6′-dithio dinicotinate, 4, 4′-di (1, 2, 3-triazolyl) disulfide hydrate, glutathione, 3-(2-pyridyl dithio) propionate N-succinimidyl, 4-(2-benzothiazolyi dithio) morpholine, 2, 2′-dibenzothiazolyl disulfide, O-isobutyloyl thiamine disulfide, aneurine disulfide, diphenyl disulfide, di-p-tolyl disulfide, bis (4-hydroxy phenyl) disulfide, 3, 3-dithio bis (1-propane sulfonic acid), 4, 4′-dithio dianiline, 2, 2′-dithio dianiline, bis (3-hydroxy phenyl) disulfide, bis (6-hydroxy-2-naphthyl) disulfide, bis (4-nitro phenyl) disulfide, bis (3-nitro phenyl) disulfide, his (2-nitro phenyl) disulfide, his (2, 4-dinitro phenyl) disulfide, 2, 2′-dithio dibenzoate, 5, 5′-dithio bis (2-nitro benzoate), 2, 2′-dipyridyl disulfide, 4, 4′-dipyridyl disulfide, 2, 2′-dithio bis (5-nitro pyridine), 6, 6′-dithio dinicotinate, and salts of the above compounds can be cited. In addition, as trisulfide, diisopropyl trisulfide or the like can be cited.

In addition, more preferably, the sulfur-based compound is concretely 2, 2-dithio dianiline, 2-amino benzene thiol, 2, 2-dipyridyl disulfide, 2-mercapto pyridine, 2-mercapto pyridine N-oxide. In this way, it is possible to lower Pb concentration further by inhibiting eutectoid of Pb.

1-2. Sn Salt, Salts other than Sn

As an Sn salt contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention, it is preferable to use a first Sn salt (Sn salt (II)) and a second Sn salt (Sn salt (IV)).

As the first Sn salt (Sn salt (II)), it is not limited as below, but concretely, an organic Sn (II) sulfonate such as Sn (II) alkane sulfonate such as Sn (II) methane sulfonate, and Sn (II) alkanol sulfonate such as Sn (II) isethionate, Sn (II) sulfate, Sn (II) borofluoride, Sn (II) chloride, Sn (II) bromide, Sn (II) iodide, Sn (II) oxide, Sn (II) phosphate, Sn (II) pyrophosphate, Sn (11) acetate, Sn (III) citrate, Sn (II) gluconate, Sn (II) tartrate, Sn (II) lactate, Sn (II) succinate, Sn (II) sulfamate, Sn (II) formate, Sn (II) silicofluoride, and else, can be cited.

As the second Sn salt (Sn salt (IV)), it is not limited as below, but concretely, sodium stannate, kalium stannate, and else, cane be cited.

Especially, the organic Sn (II) sulfonate such as Sn (II) alkane sulfonate such as Sn (III) methane sulfonate, and Sn (II) alkanol sulfonate such as Sn (II) isethionate, is preferable.

In addition, a concentration of the Sn salt is preferably 5 to 100 g/L. If it is less than 5 it might be a cause for occurring a burning or a scorch as Sn concentration is too low. On the other hand, if it is more than 100 g/L, there is a problem of an increase in a cost, and a stability of a bath becomes unstable, so there is a possibility for occurring precipitation. More preferably, it is 10 to 70 g/L.

Further, it is possible to use an Sn salt with low Pb concentration, for example with Pb concentration of 1.0 ppm or less. It will be a plating solution especially for obtaining an Sn plated article with low Pb concentration, and it is possible to lower Pb concentration further. Typical Sn salt and concentration are materials and concentrations cited in the above.

In addition, it can be applied not only for Sn plating, but also for Sn alloy plating. In other words, it is preferable that the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention further comprises one or more types of metal salts other than Sn salt selected from Ag salt, Cu salt, Bi salt, In salt, Au salt, Sb salt, Zn salt, Ni salt, or the like. In this way, it will be an Sn alloy plating solution also applicable for Sn alloy plating (SnAg, SnCu, SnBi, SnIn, SnAu, SnSb, SnZn, SnNi, or the like), other than Sn plating, and it is possible to provide the Sn alloy plating solution capable of lowering Pb concentration.

1-3. Acids or Water-Soluble Salts Thereof

Acids or water-soluble salts thereof contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention are one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof. The acids or water-soluble salts thereof are contained for assisting inhibition of eutectoid of Pb. It is because pH of Sn surface or a surface of an article to be plated will be maintained constantly, and it will be uniform surface potential, by the acids or water-soluble salts thereof.

As the acids or water-soluble salts thereof, it is not limited as below, but concretely, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, organic sulfonic acid (alkane sulfonate such as methane sulfonate, and alkanol sulfonate such as isethionate), carboxylic acid (aromatic carboxylic acid, saturated aliphatic carboxylic acid, amino carboxylic acid), and else can be cited. According to need, it is possible to use neutralized salts of the water-soluble salts.

In addition, a concentration of the acids or water-soluble salts thereof is preferably 50 to 500 g/L. If it is less than 50 g/L, a stability of the plating solution will be deteriorated, and precipitates tend to occur. There is a possibility to have an influence on Pb deposition potential. On the other hand, if it is more than 500 g/L, cost will be increased. More preferably, it is 50 to 300 g/L, further preferably, it is 100 to 200 g/L.

1-4. Surfactant

As a surfactant contained in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention, it is possible to use one or more types of surfactants selected from anionic surfactant, cationic surfactant, and non-ionic surfactant. Above all, the non-ionic surfactant is preferable, and alkylene oxide-based surfactant is suitable. The surfactant is contained for assisting inhibition of eutectoid of Pb. It is because the surfactant uniforms a current density of an Sn or Sn alloy crystal surface or an article to be plated, and maintains uniform deposition potential at the surface.

As the alkylene oxide-based surfactant, it is not limited as below, but concretely, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene aliphatic ester, polyoxyethylene multivalent alcohol ether, ethylene oxide propylene oxide block polymer type, ethylene oxide propylene oxide random polymer type, propylene oxide polymer type, and else, can be cited. Above all, especially, polyoxyethylene alkyl phenyl ether is preferable.

In addition, it is preferable that the acids or water-soluble salts thereof is one or more types of acids or salts thereof selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, organic sulfonic acid, carboxylic acid, or salt thereof, and also, the surfactant includes one or more types of surfactants selected from anionic surfactant, cationic surfactant, and non-ionic surfactant.

In addition, a concentration of the surfactant is preferably 0.05 to 100 g/L. If it is less than 0.05 g/L, there is a case that a burning or a scorch occurs at a part to be high current density, when it is plated at high current density in order to decrease plating time. On the other hand, if it is more than 100 g/L, Sn plating film will be blackened, and there is a case that a defect such as uneven color occurs. Thus, it might have an influence on a film of an Sn or Sn alloy plating itself. More preferably, it is 0.5 to 100 g/L.

As mentioned above, the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention at least comprises: the sulfur-based compound; the Sn salt; one or more types of the acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and the surfactant. By containing the above components in the plating solution as described above, it will be most suitable for inhibiting eutectoid of Pb, as the plating surface with uniform deposition potential will be achieved by each component. In addition, it will be difficult to achieve the above purpose, if one constituent or component is missing.

It was explained at least about the above constituents and components, but it is preferable that the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention further comprises following constituents and components. It is explained in below.

1-5. Crystal Regulator

It is preferable that the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention further comprises a crystal regulator. The crystal regulator is having an effect to smoothen a deposited film. Thus, when an Sn or Sn alloy crystal is growing, it assists to inhibit eutectoid of Pb by reducing a bias of local potential of crystal surface, by further smoothening the Sn or Sn alloy crystal. In addition, as the crystal regulator, aldehydes, ketones, benzothiazoles, or the like, can be used.

1-6. Organic Solvent

It is preferable that the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention further comprises an organic solvent. In addition, as the organic solvent, it is not limited as below, but concretely, monovalent alcohols such as methanol, 2-propanol, bivalent alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, and else, can be cited.

1-7. Antioxidant

It is preferable that the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention further comprises an antioxidant. The antioxidant is having an effect to stabilize the solution by inhibiting oxidation of bivalent Sn ions in a bath, and by inhibiting oxidation of other components in the plating solution. Thus, by comprising the antioxidant, it assists to maintain oxidation-reduction potential of Sn more constant, so as a result, it can assist to inhibit eutectoid of Ph. As the antioxidant, it is not limited as below, but concretely, catechol, hydroquinone, 4-methoxy phenol, ascorbic acid, and else, can be cited.

In addition, it is preferable that a concentration of the antioxidant is 0.1 to 100 g/L. If the concentration is less than 0.1 g/L, an oxidation inhibiting effect may be decreased. On the other hand, if the concentration is more than 100 g/L, the cost tends to increase. Further preferable range is 0,1 to 10 g/L.

1-8. Chelating Agent

The electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention can further comprise a chelating agent. As the chelating agent, it is not limited as below, but concretely, oxalic acid, succinic acid, malonic acid, glycolic acid, glconic acid, gluconolactone, glycine, ethylene diamine acetate, pyrophosphoric acid, tripolyphosphate, and else, can be cited.

In addition, it is preferable that a concentration of the chelating agent is 0.1 to 200 g/L. If it is less than 0.1 g/L, a chelating effect may be decreased. On the other hand, if it is more than 200 g/L, the cost tends to increase. Further preferable range is 0.1 to 100 g/L.

2. Method for Producing Sn or Sn Alloy Plated Article

As illustrated in FIG. 1, a method for producing an Sn or Sn alloy plated article relating to one embodiment of the present invention is a method for producing an Sn or Sn alloy plated article for producing a plated article for solder bonding, comprising: a plating solution preparation step S1 for preparing an electrolytic Sn or Sn alloy plating solution; and a plating step S2 for producing the Sn or Sn alloy plated article using the plating solution. Hereinafter, explaining in an order of steps.

2-1. Plating Solution Preparation Step

As illustrated in FIG. 1, a method for producing an Sn or Sn alloy plated article relating to one embodiment of the present invention comprises a plating solution preparation step S1. In the plating solution preparation step S1, the electrolytic Sn or Sn alloy plating solution is prepared by at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant. And, the sulfur-based compound is a thiol compound represented by following general formula (Formula A), a salt of the thiol compound (Formula A), or a disulfide compound (Formula B).

HS—R₁   Formula A:

R₇—S—S—R₇   Formula B:

R₁ is any of

R₂ is any of

The sulfur-based compound contained in the plating solution used in the method for producing the Sn or Sn alloy plated article relating to one embodiment of the present invention is contained as an eutectoid inhibitor of Pb, which is a thiol compound, a salt of the thiol compound, as indicated in the Formula A, or a disulfide compound as indicated in the Formula B. And, R₁ is any of aniline (I), pyridine (II), or pyridine N oxide (III). In addition, R₂ is any of aniline (IV), pyridine (V), benzene (VI), butane (VII), or toluene (VIII).

By preparing a plating solution at least comprising the Sn salt, the acids or water-soluble salts thereof, and the surfactant, as described in the above, it is possible to provide the Sn or Sn alloy plated article capable of lowering Pb concentration, by inhibiting eutectoid of Pb, by functions of each component.

In addition, preferable compounds, a concentration, and a ratio of concentration of the sulfur-based compound, the Sn salt, the acids or water-soluble salts thereof, and the surfactant are as explained in the above. In addition, as the Sn salt, it is possible to use the Sn salt with Pb concentration of 1.0 ppm or less. It is preferable to further comprise the crystal regulator, the organic solvent, the antioxidant, and the chelating agent, in addition to the sulfur-based compound, the Sn salt, the acids or water-soluble salts thereof, and the surfactant. In order to be the Sn alloy plating solution, as described in the above, it is preferable to comprise one or more types of metal salts other than Sn salt selected from Ag salt, Cu salt, Bi salt, In salt, Au salt, Sb salt, Zn salt, Ni salt, or the like.

2-2. Plating Step

As illustrated in FIG. 1, a method for producing an Sn or Sn alloy plated article relating to one embodiment of the present invention comprises a plating step S2. The Sn or Sn alloy plated article is produced using the plating solution prepared in the plating solution preparation step S1. It is not limited particularly, but it is preferable to perform plating with a current density in a range of 1 to 20 A/dm², Further preferable range is 2 to 6 A/dm². In addition, necessary pretreatment and posttreatment are performed to obtain the Sn or Sn alloy plated article.

In addition, according to the method for producing an Sn or Sn alloy plated article, a film of the plated article is low alpha grade Sn or Sn alloy plating film (less than 0.01 counts/hr/cm²). Here, a relation of an amount of alpha ray (counts/hr/cm²) and Pb content in Sn is illustrated in FIG. 2. As illustrated, an amount of alpha ray and Pb content in Sn are in proportional relation, and when the Pb content increases, the amount of alpha ray increases. By calculating approximation from these data, it is amount of alpha ray (counts/hr/cm²)=0.0048*Pb content (ppm)+0.0005. From this approximation, Pb content corresponding to 0.01 counts/hr/cm² is 2.0 ppm. In other words, the low alpha grade Sn or Sn alloy plating film is having a Ph concentration of 2.0 ppm or less. In this way, it is possible to lower Pb concentration, and it is possible to prevent an influence for malfunction of the device.

EXAMPLES

Next, explaining in detail about an electrolytic Sn or Sn alloy plating solution and a method for producing an Sn or Sn alloy plated article relating to one embodiment of the present invention by using examples. In addition, the present invention is not limited to these examples.

Example 1

In an example 1, as an electrolytic Sn plating solution, a sulfur-based compound, an Sn salt, an organic acid, and a surfactant were added. As the sulfur-based compound, 5 g/L of dibenzyl disulfide was added. As the Sn salt, 40 g/L of Sn (II) alkane sulfonate was added as Sn (Sn²⁺). As the organic acid, 155.3 g/L, of organic sulfonic acid was added. As the surfactant, 5 g/L of polyoxyethylene alkyl phenyl ether was added. In addition, as the crystal regulator, 0.15 g/L of 2-mercapto benzothiazole was added. A solution temperature of the plating solution was 30° C., and a current density was 4 A/dm². Further, in the example 1, a plating solution using an Sn salt with low Pb concentration of 1.0 ppm or less was also prepared.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 15.454 ppm, and. Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured. In addition, hereinafter, the eutectic amount of Pb when using the Sn salt was measured using A3300 made by Hitachi High-Tech Science Corporation, and the eutectic amount of Ph when using the Sn salt with low Pb concentration was measured using ICP-MS of Agilent 7700 Series made by Agilent Technologies. In addition, the deposition potential was measured using model 2325 bipotentiostat made by BAS Inc.

Example 2

In an example 2, as the sulfur-based compound, 5 with of 4, 4′-dipyridyl disulfide was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Ph concentration in raw material metal Sn of the Sn salt was 15.454 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 3

In an example 3, as the sulfur-based compound, 5 g/L of diphenyl disulfide was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Ph concentration in raw material metal Sn of the Sn salt was 15.454 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 4

In an example 4, as the sulfur-based compound, 5 g/L of 2, 2-dithio dianiline was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 25.885 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Ph concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 5

In an example 5, as the sulfur-based compound, 5 g/L of 2-amino benzene thiol was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 15.454 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 6

In an example 6, as the sulfur-based compound, 5 g/L of 2, 2-dipyridyl disulfide was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Ph concentration in raw material metal Sn of the Sn salt was 26.236 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 7

In an example 7, as the sulfur-based compound, 5 of 2-mercapto pyridine was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 15.454 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Ph concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 8

In an example 8, as the sulfur-based compound, 5 g/L of 2-mercapto pyridine N oxide Na salt was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 15.454 ppm, and. Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 9

In an example 9, as the sulfur-based compound, 5 g/L of 2, 2-dithio dianiline was added. Further, 0.5 g/L of Ag salt was added, in order to be Sn—Ag alloy plating. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 40.301 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.826 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Example 10

In an example 10, as the sulfur-based compound, 5 g/L of 2, 2-dipyridyl disulfide was added. Further, 0.5 gat of Ag salt was added, in order to be Sn—Ag alloy plating. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 65.431 ppm, and. Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Comparative Example 1

In a comparative example 1, the sulfur-based compound was not added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 25.807 ppm. and Ph concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Comparative Example 2

In a comparative example 2, as a sulfur-based compound, 5 g/L of 3, 6-dithia 1, 8-octanediol was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 21.584 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Ph, and a deposition potential were measured.

Comparative Example 3

In a comparative example 3, as a sulfur-based compound, 5 gat of thiourea was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 16.794 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Comparative Example 4

In a comparative example 4, as a sulfur-based compound, 5 g/L of bis (2-amino phenyl) sulfide was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time. Pb concentration in raw material metal Sn of the Sn salt was 15.065 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Pb concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Ph, a eutectic amount of Pb, and a deposition potential were measured.

Comparative Example 5

In a comparative example 5, as a sulfur-based compound, 5 g/L of 3-amino pyridine was added. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1. In addition, in the comparative example 5, a plating solution using the Sn salt with low Ph concentration was not prepared.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 16.068 ppm.

And, by using the above plating solution, electrolytic Sn plating was performed, and a eutectic ratio (%) of Pb and a eutectic amount of Pb were measured.

Comparative Example 6

In a comparative example 6, as the sulfur-based compound, 5 g/L of 2, 2-dithio dianiline was added as in the example 4, but the organic acid and the surfactant were not added. In addition, conditions of the Sn salt, the crystal regulator, the solution temperature, and the current density were same as the example 1.

Comparative Example 7

In a comparative example 7, as the sulfur-based compound, 5 g/L of 2, 2-dithio dianiline was added as in the example 4, but the surfactant was not added. In addition, conditions of the Sn salt, the organic acid, the crystal regulator, the solution temperature, and the current density were same as the example 1.

Comparative Example 8

In a comparative example 8, as a sulfur-based compound, 5 g/L of 3, 6-dithia 1, 8-octanediol was added. Further, 0.5 g/L of Ag salt was added, in order to be Sn—Ag alloy plating. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 26.734 ppm, and Pb concentration in raw material metal Sn of the Sn salt with low Ph concentration was 0.407 ppm.

And, by using the above two plating solutions, electrolytic Sn plating was performed respectively, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

Comparative Example 9

In a comparative example 9, as a sulfur-based compound, 5 g/L of thiourea was added. Further, 0.5 g/L of Ag salt was added, in order to be Sn—Ag alloy plating. In addition, conditions of the Sn salt, the organic acid, the surfactant, the crystal regulator, the solution temperature, and the current density were same as the example 1. in addition, in the comparative example 9, a plating solution using the Sn salt with low Ph concentration was not prepared.

At this time, Pb concentration in raw material metal Sn of the Sn salt was 25.807 ppm.

And, by using the above plating solution, electrolytic Sn plating was performed, and a eutectic ratio (%) of Pb, a eutectic amount of Pb, and a deposition potential were measured.

In addition, the eutectic ratio (%) of Pb was calculated as Pb content (ppm) in plating film/Pb content (ppm) in Sn raw material*100. The results were illustrated in Table 1.

TABLE 1 Examples/ Comparative Composition examples Compound Structure Sn plating Sn: 40 g/L Organic Sulfenic acid 155 Jg/L Polyoxyethylene alkyl phenyl ether: 5 g/L Crystal regulator (2-mercapto benzothiazole): 0.15 g/L + compound described in right 5 g/L (However, comparative example 6 does not comprise organic sulfonic acid and polyoxyethylene alkyl phenyl ether. Also, comparative example 7 does not comprise polyoxyethylene alkyl phenyl ether.) Example 1         Example 2       Example 3         Dibenzyl disulfide         4, 4′-dipyridyl disulfide       Diphenyl disulfide        

 

 

  Example 4 2, 2-dithio dianiline

Example 5 2-emino benzene thiol

Example 6 2, 2-dipyridyl disulfide

Example 7 2-mercapto pyridine

Example 8 2-mercapto pyridine N oxide Na salt

Comparative None example 1 Comparative example 2 3, 6-dithia 1, 8-octanediol

Comparative example 3 Thiourea

Comparative example 4 Bis (2-amino phenyl) sulfide

Comparative example 5 3-amino pyridine

Comparative example 6 2, 2-dithio dianiline

Comparative example 7 2, 2-dithio dianiline

Sn—Ag Sn: 40 g/L, Ag: 0.5 g/L Organic Sulfenic acid 115 mL/L Polyoxyethylene alkyl phenyl ether: 5 g/L Crystal regulator (2-mercapto benzothiazole): 0.15 g/L + compound described in right 5 g/L Example 9 2, 2-dithio dianiline

Example 10 2, 2-dipyridyl disulfide

Comparative example 8 3, 6-dithia 1, B-octanediol

Comparative example 9 Thiourea

Sn Salt Pb Eutectic Examples/ concentration amount. Pb Comparative (ppm) in Sn raw Eutectic concentration Composition examples material metal ration (%) (ppm) in metal Sn plating Example 1 15.454 48.7% 7.5 Sn: 40 g/L Example 2 15.454 72.1% 11.1 Organic Sulfenic acid 155 Jg/L Example 3 15.454 56.2% 8.7 Polyoxyethylene alkyl phenyl ether: Example 4 25.885 35.2% 9.1 5 g/L Example 5 15.454 21.5% 3.3 Crystal regulator Example 6 26.236 3.6% 0.9 (2-mercapto benzothiazole): 0.15 g/L Example 7 15.454 12.0% 1.9 + compound described in right Example 8 15.454 7.1% 1.1 5 g/L Comparative 26.807 330.2% 85.2 (However, comparative example 6 example 1 does not comprise organic sulfonic Comparative 21.584 316.0% 68.2 acid and polyoxyethylene alkyl example 2 phenyl ether.Also, comparative Comparative 16.794 221.7% 37.2 example 7 does not comprise example 3 polyoxyethylene alkyl phenyl Comparative 15.065 365.3% 53.5 ether.) example 4 Comparative 16.068 248.9% 40.8 example 5 Comparative — — — example 6 Comparative — — — example 7 Sn—Ag Example 9 40.301 33.0% 13.3 Sn: 40 g/L, Ag: 0.5 g/L Example 10 65.431 0.3% 0.2 Organic Sulfenic acid 115 mL/L Comparative 26.734 270.1% 72.2 Polyoxyethylene alkyl phenyl ether: example 8 5 g/L Comparative 25.807 183.3% 47.3 Crystal regulator example 9 (2-mercapto benzothiazole): 0.15 g/ + compound described in right 5 g/L Sn salt with low Pb concentration Pb

Examples/ concenttration amount, Pb Comparative (ppm) in Sn raw Eutectic concentration Composition examples material metal ration (%) (ppm) in metal Sn plating Example 1 0.407 97.0% 0.39 Sn: 40 g/L Example 2 0.407 113.0% 0.46 Organic Sulfenic acid 155 Jg/L Example 3 0.407 103.0% 0.42 Polyoxyethylene alkyl phenyl ether: Example 4 0.407 70.0% 0.28 5 g/L Example 5 0.407 86.0% 0.35 Crystal regulator Example 6 0.407 11.0% 0.04 (2-mercapto benzothiazole): 0.15 g/L Example 7 0.407 15.0% 0.06 + compound described in right Example 8 0.407 8.0% 0.03 5 g/L Comparative 0.407 351% 1.43 (However, comparative example 6 example 1 does not comprise organic sulfonic Comparative 0.407 286.0% 1.16 acid and polyoxyethylene alkyl example 2 phenyl ether.Also, comparative Comparative 0.407 233.0% 0.95 example 7 does not comprise example 3 polyoxyethylene alkyl phenyl Comparative 0.407 388.0% 1.58 ether.) example 4 Comparative example 5 Comparative — — — example 6 Comparative — — — example 7 Sn—Ag Example 9 0.826 90.0% 0.74 Sn: 40 g/L, Ag: 0.5 g/L Example 10 0.407 9.0% 0.04 Organic Sulfenic acid 115 mL/L Comparative 0.407 292.7% 1.19 Polyoxyethylene alkyl phenyl ether: example 8 5 g/L Comparative Crystal regulator example 9 (2-mercapto benzothiazole): 0.15 g/L + compound described in right 5 g/L Deposition potential (V) Potential difference Examples/ (Sp − PB) in minus: Comparative priority on Sn Composition examples Pb Sn deposition Sn plating Example 1 −0.043 −0.111 −0.068 Sn: 40 g/L Example 2 −0.088 −0.172 −0.084 Organic Sulfenic acid 155 Jg/L Example 3 −0.013 −0.068 −0.075 Polyoxyethylene alkyl phenyl ether: Example 4 −0.072 −0.135 −0.063 5 g/L Example 5 −0.061 −0.135 −0.074 Crystal regulator Example 6 −0.132 −0.236 −0.104 (2-mercapto benzothiazole): 0.15 g/L Example 7 −0.120 −0.203 −0.077 + compound described in right Example 8 −0.111 −0.221 −0.110 5 g/L Comparative 0.008 −0.006 −0.011 (However, comparative example 6 example 1 does not comprise organic sulfonic Comparative 0.233 0.208 −0.025 acid and polyoxyethylene alkyl example 2 phenyl ether.Also, comparative Comparative 0.138 0.152 0.014 example 7 does not comprise example 3 polyoxyethylene alkyl phenyl Comparative −0.023 0.008 0.031 ether.) example 4 Comparative example 5 Comparative — — — example 6 Comparative — — — example 7 Sn—Ag Example 9 −0.072 −0.135 −0.063 Sn: 40 g/L, Ag: 0.5 g/L Example 10 −0.132 −0.236 −0.104 Organic Sulfenic acid 115 mL/L Comparative 0.238 0.208 −0.025 Polyoxyethylene alkyl phenyl ether: example 8 5 g/L Comparative 0.138 0.152 0.014 Crystal regulator example 9 (2-mercapto benzothiazole): 0.15 g/ + compound described in right 5 g/L

indicates data missing or illegible when filed

In all examples, values of eutectic ratio of Ph were lower than which of all comparative examples, and values of eutectic amount of Pb were lower than which of all comparative examples. Further, in the plating solutions of all examples using the Sn salt with low Pb concentration, values of eutectic ratio of Pb were lower than which of all comparative examples, and values of eutectic amount of Pb were significantly lower than which of all comparative examples. In addition, in the examples adding the sulfur-based compound used in the electrolytic Sn plating solution relating to one embodiment of the present invention, the deposition potential of Pb and Sn were shifted to noble or base, and a deposition potential difference of Pb and Sn were broadened to 0.06 V or more, compared to the comparative examples. Thus, it was understood that the sulfur-based compound functioned as the eutectoid inhibitor of Pb.

In addition, in the examples 4 to 7, in which the sulfur-based compound in which the Formula A or the Formula B is bonded with 2-position or 6-position of the R₁ or the R₂, i.e. 2, 2-dithio dianiline, 2-amino benzene thiol, 2, 2-dipyridyl disulfide, 2-mercapto pyridine, or 2-mercapto pyridine N oxide Na salt, is added, values of eutectic ratio of Pb were lower compared to the examples 1 to 3, in which the Formula A or the Formula B is bonded with other than 2-position or 6-position of the R₁ or the R₂, in the plating solution of the Sn salt and in the plating solution using the Sn salt with low Pb concentration.

In the comparative example 6 in which the organic acid and the surfactant were not added, and in the comparative example 7 in which the surfactant was not added, a film was not formed, so it was not possible to measure the eutectic ratio of Pb and the Pb concentration. As a reason that a film was not formed, it is considered that it is because uniform surface potential was not achieved as pH of a surface to be plated and an Sn surface were not maintained constantly, and that it is because uniform deposition potential was not maintained at the surface as current density of an article to be plated and an Sn crystal surface were not uniform. Thus, it is important to add the inorganic acid, the organic acid or water-soluble salt thereof and the surfactant in addition to the sulfur-based compound and the Sn salt, and it was important to combine with the sulfur-based compound.

In addition, also in the Sn—Ag alloy plating solution, in the examples 9 and 10, values of eutectic ratio of Ph were lower than which of the comparative examples 8 and 9, and values of eutectic amount of Pb were lower than which of the comparative examples 8 and 9. Further, in the plating solutions of all the examples using the Sn salt with low Pb concentration, values of eutectic ratio of Pb were lower than which of all comparative examples, and values of eutectic amount of Pb were significantly lower than which of all comparative examples. In addition, in the examples adding the sulfur-based compound used in the electrolytic Sn or Sn alloy plating solution relating to one embodiment of the present invention, the deposition potential of Pb and Sn were shifted to noble or base, and a deposition potential difference of Ph and Sn were broadened to 0.06 V or more, compared to the comparative examples. Thus, it was understood that the sulfur-based compound functioned as the eutectoid inhibitor of Pb.

By applying the electrolytic Sn or Sn alloy plating solution and the method for producing the Sn or Sn alloy plated article relating to one embodiment of the present invention, it was possible to provide the electrolytic Sn or Sn alloy plating solution capable of lowering Pb concentration, by inhibiting eutectoid of Ph, by functions of each component.

In addition, it is explained in detail about each embodiment and each example of the present invention as the above, but it can be understood easily for those who skilled in the art that various modifications can be made without practically departing from new matters and effect of the present invention. Therefore, all such variants should be included in the scope of the present invention.

For example, terms described with different terms having broader or equivalent meaning at least once in description and drawings can be replaced with these different terms in any part of description and drawings. In addition, operation and configuration of the X-ray fluorescence analysis measurement method and the X-ray fluorescence analysis measurement device are not limited to those explained in each embodiment and each example of the present invention, and various modifications can be made.

GLOSSARY OF DRAWING REFERENCES

-   S1 Plating solution preparation step -   S2 Plating step 

1. An electrolytic Sn or Sn alloy plating solution for forming a plated article for solder bonding, at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant, wherein the sulfur-based compound is a thiol compound represented by following general formula (Formula A), a salt of the thiol compound (Formula A), or a disulfide compound (Formula B). HS—R₁   Formula A: R₂—S—S—R₂   Formula B: R₁ is any of

R₂ is any of


2. The electrolytic Sn or Sn alloy plating solution according to claim 1, wherein a ratio of concentration of the sulfur-based compound, Sn of the Sn salt, the acids or water-soluble salts thereof, and the surfactant is 1:0.2 to 700:1 to 3000:0.01 to 1000 by weight ratio.
 3. The electrolytic Sn or Sn alloy plating solution according to claim 1, wherein the R₁ is any of the general formulas (I) to (III), the R₂ is the general formula (IV) or (V), and the Formula (A) or the Formula (B) is bonded with 2-position or 6-position of the R₁ or the R₂.
 4. The electrolytic Sn or Sn alloy plating solution according to claim 1, wherein the acids or water-soluble salts thereof are one or more types of acids or salts thereof selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, organic sulfonic acid, carboxylic acid, or salt thereof, and also, the surfactant includes one or more types of surfactants selected from anionic surfactant, cationic surfactant, and non-ionic surfactant.
 5. The electrolytic Sn or Sn alloy plating solution according to claim 1, further comprising one or more types of metal salts other than Sn salt selected from Ag salt, Cu salt, Bi salt, In salt, Au salt, Sb salt, Zn salt, and Ni salt.
 6. A method for producing an Sn or Sn alloy plated article for producing a plated article for solder bonding, comprising: a plating solution preparation step for preparing an electrolytic Sn or Sn alloy plating solution; and a plating step for producing the Sn or Sn alloy plated article using the plating solution, wherein, in the plating solution preparation step, the electrolytic Sn or Sn alloy plating solution is prepared by at least comprising: a sulfur-based compound; an Sn salt; one or more types of acids or water-soluble salts thereof selected from inorganic acid, organic acid or water-soluble salt thereof; and a surfactant, wherein the sulfur-based compound is a thiol compound represented by following general formula (Formula A), a salt of the thiol compound (Formula A), or a disulfide compound (Formula B). HS—R₁   Formula A: R₂—S—S—R₂   Formula B: R₁ is any of

R₂ is any of


7. The method for producing the Sn or Sn alloy plated article according to claim 6, wherein a film of the Sn or Sn alloy plated article is low alpha grade Sn or Sn alloy plating film (less than 0.01 counts/hr/cm²).
 8. The electrolytic Sn or Sn alloy plating solution according to claim 2, wherein the R₁ is any of the general formulas (I) to (III), the R₂ is the general formula (IV) or (V), and the Formula (A) or the Formula (B) is bonded with 2-position or 6-position of the R₁ or the R₂.
 9. The electrolytic Sn or Sn alloy plating solution according to claim 2, wherein the acids or water-soluble salts thereof are one or more types of acids or salts thereof selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, organic sulfonic acid, carboxylic acid, or salt thereof, and also, the surfactant includes one or more types of surfactants selected from anionic surfactant, cationic surfactant, and non-ionic surfactant.
 10. The electrolytic Sn or Sn alloy plating solution according to claim 2, further comprising one or more types of metal salts other than Sn salt selected from Ag salt, Cu salt, Bi salt, In salt, Au salt, Sb salt, Zn salt, and Ni salt. 